Vehicle identification means are used around the world, mostly by law enforcement authorities and in conjunction with various kinds of law enforcement activities, such as, but not limited to speed-traps.
Existing speed-traps fall into two main categories: active speed-traps and passive speed-traps.
Active traps operate by transmitting a signal towards a traveling vehicle and measuring time delay, Doppler effect or other parameters to measure the speed of the vehicle. Active traps typically use radar or laser light for detection. Examples include Digital SMARTCAM, provided by Redflex, of Melbourne, Australia and Moltanova F-6 photo radars, provided by Multanova AG, Seestr. 110, CH-8610 Uster, www.multanova.ch, which record license plate numbers on film, and digital cameras, which store or transmit license plate numbers electronically. Active speed-traps may operate from fixed or mobile locations.
Passive traps operate by identifying a traveling vehicle in two positions and calculating the vehicle's speed using the known distance between the two positions and the time used by the vehicle to travel between them. Passive traps may also use film and/or digital cameras to capture the license plate number.
Other uses of vehicle identification means exist, which are not aimed at speed violations but at various other types of law violations, such as traversing in red light, not keeping an appropriate distance from the vehicle in front, etc. These VIMs use photographic means for capturing the license plate. Examples are MegaCar and CarFlow, available from MegaPixel, Russia.
A number of methods are known for locating a speed-trap. One such method uses an apparatus, such as an RF antenna, for detecting radar signals from a radar-operated speed trap and alerts the driver accordingly. There are several drawbacks to this method. First, the driver is only alerted once the radar beam from the speed trap is incident on his vehicle, which may be too late for reducing his speed. Second, the radar detector may be falsely set-off by devices other than speed-traps, which operate on similar frequencies.
Another method for detecting speed-traps, such as used by Photo-LIDAR, available from Ingram Technologies of Utah, USA, uses laser detectors to detect incident light from active speed-traps using laser light. Similar to radar detectors, the laser detector also alerts the driver only when a laser beam is incident on his vehicle and will not detect speed-traps using other detection methods.
An additional method for detecting speed-traps, which overcomes the shortcomings of the first two methods, uses a combination of a speed-trap location database and a Global Positioning System (GPS) to alert the driver that he is approaching a speed-trap. Various systems of this type are described, for example, in International Published Application WO 01/55744 and in UK Published Applications UK 2353647 and UK 2353650. Existing products using this method include Geodesy GPS SpeedTrap Location System, manufactured by Morpheous, UK, and GPS Warning System available from Origin blue I, UK.
All the above disclosures and products use an updateable database of speed-trap location coordinates, get continuous location readings from the GPS and alert the driver, by various means such as voice alert, beep alert or displayed warning, when he is within a certain range of a speed-trap. The disclosed devices may also determine whether the vehicle is moving in the direction of the speed-trap and only issue an alert if this is the case.
For all the detection and alert systems described above to be effective, the driver is expected to stay alert to the warning signal and reduce his speed accordingly when the signal has been issued. This requires the driver to divide some of his attention from the road. The driver may be tired, or in the middle of a conversation, and not pay attention to the warning signal.
Various active counter-measures for evading speed traps exist in the marketplace, including means for detecting and/or jamming radar signals, in order to avoid detection. The jamming devices, such as the Phantom Radar Jammer, manufactured by Galaxy Descramblers of Illinois, USA, receive the radar gun's signal and piggyback it with noise, so that the signal going back to the radar gun is not recognized by the computer.
Other existing means deal with obscuring the vehicle's license plate from the photo-radar camera. These products, such as the Protector, manufactured by On-Track Manufacturing Corp. of Blaine, Wash., use especially designed license plate covers, comprising a micro-prismatic lens, which bends light like a prism when viewed from a 35° angle. This effect makes the cover reflect the incoming light from the camera's flash, when impinging at 350 horizontally or vertically, with an additional configuration that combines partial horizontal and vertical reflection. The cover looks transparent when viewed from directly behind (or in front of) the vehicle. The effective protection of these products is limited by the narrow angle of protection.
Another product, manufactured by Chimera of New Haven, Conn., provides a different type of micro-prismatic lens, designed to reflect incoming light starting at a predefined angle of 45° and covering the entire range from the starting angle to 180°. The drawback of this type of lens is that it is visible from various angles.
U.S. Pat. No. 4,956,930 to Troncoso describes a license plate cover provided with vanes, designed to obscure viewing of the plate identification from the side.
The drawback of all these counter-measure devices lies in their non-selective use. The measures are permanently operational and thus place the driver in permanent danger of being apprehended.
Published U.S. patent application Ser. No. 2002/0022920 provides a system including a positional sensor such as a GPS device. Position information is used to access a database of speed limit and/or speed trap information. Speed limit information is used to control the speed of the automobile as part of a cruise control operation and/or is used to provide the motor vehicle operator with warnings.
There is need for an active, universal law enforcement vehicle trap detection system that will be effective against all types of vehicle law enforcement traps and will automatically, upon detecting approach to a trap, operate identification prevention measures to avoid detection of the vehicle or the driver, without the need for the driver to be alert and without reducing the vehicle's cruising speed, and automatically deactivate the identification prevention measures when the vehicle is out of the detection zone.